There are two general types of cyclic AMP-dependent protein kinases, type I and type II, which may fulfill different biological functions. The long-term goal of the proposed research is a delineation of the differences between the cyclic AMP binding sites on the regulatory subunits of these two types of kinases. This will be done by examining the ability of a number of carefully chosen cyclic AMP analogs to interact with type I and type II kinases from various sources. These analogs will be of two types: (1) those in which one of the atoms of the cyclic AMP molecule has been either removed or replaced by a different type of atom, and (2) those in which a substituent group has been covalently attached to one of the atoms of the cyclic AMP molecule. These analogs will be assayed in two ways: (1) for their ability to stimulate the catalytic activity of the protein kinases and (2) for their ability to compare with cyclic AMP for the cyclic AMP binding site on the regulatory subunit of the protein kinase.